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Find 
lim_(x rarr4)(2-sqrt(4x-12))/(x-4).
Choose 1 answer:
(A) 2
(B) 1
(c) -1
(D) The limit doesn't exist

Find limx424x12x4 \lim _{x \rightarrow 4} \frac{2-\sqrt{4 x-12}}{x-4} .\newlineChoose 11 answer:\newline(A) 22\newline(B) 11\newline(C) 1-1\newline(D) The limit doesn't exist

Full solution

Q. Find limx424x12x4 \lim _{x \rightarrow 4} \frac{2-\sqrt{4 x-12}}{x-4} .\newlineChoose 11 answer:\newline(A) 22\newline(B) 11\newline(C) 1-1\newline(D) The limit doesn't exist
  1. Substitution Check: First, let's try to directly substitute x=4x = 4 into the limit expression to see if it results in an indeterminate form.\newlinelimx424x12x4\lim_{x \to 4}\frac{2 - \sqrt{4x - 12}}{x - 4}\newline=2441244= \frac{2 - \sqrt{4\cdot4 - 12}}{4 - 4}\newline=216120= \frac{2 - \sqrt{16 - 12}}{0}\newline=240= \frac{2 - \sqrt{4}}{0}\newline=220= \frac{2 - 2}{0}\newline=00= \frac{0}{0}\newlineThis is an indeterminate form, so we cannot directly evaluate the limit by substitution.
  2. Algebraic Manipulation: Since we have an indeterminate form of 0/00/0, we need to use algebraic manipulation to simplify the expression. We can multiply the numerator and the denominator by the conjugate of the numerator to eliminate the square root.\newlineThe conjugate of the numerator 24x122 - \sqrt{4x - 12} is 2+4x122 + \sqrt{4x - 12}. We will multiply both the numerator and the denominator by this conjugate.\newlinelimx4(24x12)(2+4x12)(x4)(2+4x12)\lim_{x \to 4}\frac{(2 - \sqrt{4x - 12})(2 + \sqrt{4x - 12})}{(x - 4)(2 + \sqrt{4x - 12})}
  3. Numerator Multiplication: Now, let's perform the multiplication in the numerator, which is a difference of squares.\newline(24x12)(2+4x12)=22(4x12)2(2 - \sqrt{4x - 12})(2 + \sqrt{4x - 12}) = 2^2 - (\sqrt{4x - 12})^2\newline=4(4x12)= 4 - (4x - 12)\newline=44x+12= 4 - 4x + 12\newline=164x= 16 - 4x
  4. Simplified Limit: We can now rewrite the limit with the simplified numerator. limx4164x(x4)(2+4x12)\lim_{x \to 4}\frac{16 - 4x}{(x - 4)(2 + \sqrt{4x - 12})}
  5. Factor Out 4-4: Notice that we can factor out a 4-4 from the numerator to cancel out the (x4)(x - 4) term in the denominator.\newlinelimx44(x4)(x4)(2+4x12)=limx442+4x12\lim_{x \to 4}\frac{-4(x - 4)}{(x - 4)(2 + \sqrt{4x - 12})} = \lim_{x \to 4}\frac{-4}{2 + \sqrt{4x - 12}}
  6. Final Substitution: Now we can directly substitute x=4x = 4 into the simplified limit expression.limx442+4412\lim_{x \to 4}\frac{-4}{2 + \sqrt{4\cdot4 - 12}}= 42+1612\frac{-4}{2 + \sqrt{16 - 12}}= 42+4\frac{-4}{2 + \sqrt{4}}= 42+2\frac{-4}{2 + 2}= 44\frac{-4}{4}= 1-1

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